The GP-HR and GP-MC loggers have a damping
facility provided on Channel 1, the first analog channel. This is provided specifically
for wind direction sensors. A wind direction vane will oscillate from side to side around
the true wind direction. For a point reading to be meaningful this osillation needs to be
damped out. The GP-HR and GP-MC loggers use a process of Incremental Smoothing to achieve
this damping.
To understand incremental smoothing we have to
look at how the logger takes readings. The Potentiometer in the Wind Direction sensor is
read by an analog to digital converter. This analog to digital converter gives readings of
0 (for 0 deg North) and 65535 (for 360 deg North) and 32767 (for 180 deg South). The
logger can smooth the data by limiting the amount the analog to digital converter value
can change in a given time period.
When we setup a logger to read wind direction on
channel 1, we can specify the amount of smoothing by entering the amount the analog to
digital converter value can change in a 2 second period. 1 degree of change is 65535/360 =
182. If we want to restrict the wind vane change to 1 degree every 2 seconds, we set the
Incremental Smoothing value to 182. This is very heavy damping. If we want to restrict the
wind vane change to 10 degrees every 2 seconds, we set the Incremental Smoothing value to
1820.
The following table showes the amount of damping
provided by the Incremental Smoothing values given.
| Damping |
Degrees
per
2 sec |
Incremental
Smoothing
Value |
| Very Heavily Damped |
1 |
182 |
| |
2 |
364 |
| |
3 |
548 |
| |
4 |
728 |
| Heavily Damped |
5 |
910 |
| |
10 |
1820 |
| |
15 |
2730 |
| Moderatly Damped |
20 |
3640 |
| |
30 |
5460 |
| |
40 |
7280 |
| Lightly Damped |
50 |
9100 |
| |
60 |
10920 |
| |
70 |
12740 |
| |
80 |
14560 |
| Very Lightly Damped |
90 |
16380 |
| No Damping |
|
0 |
The Incremental Smoothing Value is set on the
Omnilog Start Logger Screen.
There is an area at the bottom left of this screen for setting up Smoothing, Wind
Speed avarage time and the Averaging Sub Interval.
This can only be changed when the logger is being Started.
It can not be changed while the logger is running.
